The present invention generally relates to fluid cleaning compositions containing water and one or more surfactants, soaps and/or detergents. More particularly, it relates to a new and improved thickening agent containing an amide useful for thickening liquid cleaner compositions.
Illustrative examples of cleaning compositions containing a mixture of at least one surface-active agent whose viscosity characteristics may need to be modified or increased may include cosmetics, such as shampoos, shower gels or creams, as well as, liquid detergents for use in the home, e.g., dishwashing liquids, bathroom and toilet cleaners and gels, and liquid laundry detergents, to name but a few. It may be desired to modify the viscosity of these liquids by increasing the viscosity to provide thicker or thickened liquids.
It is well known that surface-active agents in a dilute mixtures produce low viscosity formulations. Whenever the mixture has a low viscosity, contact with the surface on which it is used is often undesirably short, i.e., the cleaner runs or rolls off the surface. Moreover, since the product flows more easily, it has no time to react with the surface so that the user tends to use too much of the cleaner.
In order to solve this problem, many thickening agents have been added into cleaner compositions. Among them diethanolamides that are prepared with secondary amides. These materials contain high amounts of nitrosamines which is a serious drawback because it is well known that nitrosamines are carcinogenic. Copra diethanolamides have been extensively used for this purpose since they are in a liquid form and can be easily handled at room temperature, despite the fact that they contain nitrosamines. Moreover, copra diethanolamides do not provide high viscosity mixtures except at relatively high amide concentrations.
The use of palm, copra, stearin and olein monoisopropanolamides has also been suggested, because these amides generally do not contain nitrosamines since they are prepared from primary amines. However, these amides are solid at ambient or room temperatures and therefore are difficult to handle.
Furthermore, until recently, in order to obtain a cleaning mixture with a desirably high viscosity, it has been necessary to add a large quantity of mineral salt, such as sodium chloride or magnesium sulfate. For a given quantity of thickening amide, viscosity of the overall formulation increases to a maximum as mineral salts are added and then decreases. With the type of amides used, optimum viscosity can only be achieved with relatively high quantities of mineral salts (NaCl, MgSO.sub.4). A major disadvantage associated with adding large amounts of mineral salts to the formulation is that the cleaner product is less stable at low temperature and less soft when used. These drawbacks are even greater when the mineral salt content is higher.
According to this invention, it is easy to prepare mixtures containing at least one surface-active agent, having a desirably high viscosity, having only a minimum quantity of mineral salts. More particularly, superior viscosity modification at lower salt concentrations is provided by using certain room temperature liquid amides as the thickening agent which do not contain nitrosamines.